Chromium is a potentially toxic metal occurring in water and groundwater as a result of natural and anthropogenic sources. Microbial interaction with mafic and ultramafic rocks together with geogenic processes release Cr (VI) in natural environment by chromite oxidation. Moreover, Cr (VI) pollution is largely related to several Cr (VI) industrial applications in the field of energy production, manufacturing of metals and chemicals, and subsequent waste and wastewater management. Chromium discharge in European Union (EU) waters is subjected to nationwide recommendations, which vary depending on the type of industry and receiving water body. Once in water, chromium mainly occurs in two oxidation states Cr (III) and Cr (VI) and related ion forms depending on pH values, redox potential, and presence of natural reducing agents. Public concerns with chromium are primarily related to hexavalent compounds owing to their toxic effects on humans, animals, plants, and microorganisms. Risks for human health range from skin irritation to DNA damages and cancer development, depending on dose, exposure level, and duration. Remediation strategies commonly used for Cr (VI) removal include physico-chemical and biological methods. This work critically presents their advantages and disadvantages, suggesting a site-specific and accurate evaluation for choosing the best available recovering technology.

Nitrogen (N) is a fundamental nutrient for plant growth and for the performance of biological functions. In agroecosystems, nitrogen fertilization is aimed at providing a suitable N dose for crop growth, avoiding the impoverishment or the improper enrichment of nitrogen compounds in soil. The high application of nitrogen fertilizers is the main cause of the increase in nitrate leaching and loss of the quality of natural resources (groundwater and soil). In the last decades, new sustainable technological approaches have been developed and applied on laboratory and field scales to reduce the impacts of nitrogen pollution on the environmental matrices and to improve the sustainability of agricultural management. This review highlights the results of the implementation of sustainable remediation new strategies to reduce pollution from a main agricultural contaminant (nitrate) and describes the benefits obtained from the use of these solutions in agroecosystems.

The exponential growth of the human population requires an increasing application of nitrogen (N) fertilizers, causing environmental pollution. Biochar (B) amended soil has been suggested as a sustainable agricultural practice to improve crop yield and mitigate agricultural pollutants’ contamination. Evaluating the effect of fertilization on Brassica crops, in combination with spectral analysis, may specify changes in the chemical composition of the vegetable as a result of N fertilization. This study characterized cauliflower tissues treated with N fertilizer and biochar, employing Fourier Transform Infrared spectroscopy. The experiment was conducted in cauliflower mesocosms treated with two doses of N fertilizer (130 and 260 kg N ha⁻¹) with or without B. Attenuated total reflectance fractions were used to characterize fractions of curds, leaves, stems, and roots in the infrared using a Fourier transform. Principal component analysis was performed to classify the main differences among cauliflower tissues concerning treatments. FTIR spectra of Brassica oleracea L. var. botrytis tissues were related to nitrogen-based agricultural practices. The specific molecules associated with functional groups in cauliflower tissues were phenols, amides, proteins, amines, and glucosinolates. Biochar amended soil resulted in higher peaks that correspond to the stretching of phenols and proteins. The application of sustainable nitrogen fertilizers might influence the absorption bands characteristic of cauliflower’s typical metabolites. The research allows the identification of Brassicaceae’s functional molecules with a potential agronomic application.

A laboratory-scale study was carried out to evaluate the groundwater bioremediation potential of hexavalent chromium (Cr(VI)), taking into account the chromate pollution of an industrial site located in Southern Italy (Apulia Region). The reduction of Cr(VI) was studied on laboratory microcosms, set up in different experimental conditions, namely: ABIO (soil and water sterilized), BIO (soil and water not sterilized), LATT (with the addition of lactate), and YE (with the addition of yeast extract). Control test lines, set up by using sterilized matrices and amendments, were employed to assess the occurrence of the pollutant reduction via chemical processes. By combining molecular (microbial abundance, specific chromate reductase genes (ChR) and the Shewanella oinedensis bacterial strain) with chemical analyses of chromium (VI and III) in the matrices (water and soil) of each microcosm, it was possible to investigate the response of microbial populations to different experimental conditions, and therefore, to assess their bioremediation capability in promoting Cr(VI) reduction. The overall results achieved within this work evidenced the key role of amendments (lactate and yeast extract) in enhancing the biological reduction of hexavalent chromium in the contaminated aqueous phase of laboratory microcosms. The highest value of Cr(VI) removal (99.47%) was obtained in the YE amended microcosms at seven days.

In agriculture, biochar (B) application has been suggested as a green technology to reduce nitrate pollution from agricultural origins and improve crop yield. The agronomic impact of B use on soil has been extensively studied, while knowledge of its possible effects on horticultural cultivation is still scarce. A greenhouse experiment was conducted to evaluate the effect of using biochar in soils treated with two different rates of nitrogen fertilizers on soil properties and nitrogen (N) leachate. This study also investigated the vegetative parameters during the crop growing season of Brassica oleracea L. var. botrytis. Soil mesocosms were set up to test the following treatments: untreated/control (C); normal dose of N fertilizer (130 kg N ha⁻¹) (ND); ND+B; high dose of N fertilizer (260 kg N ha⁻¹) (HD); and HD+B. Principal component analysis and cluster analysis were exploited to assess biochar’s ability to reduce nitrate leaching and enhance soil–vegetative properties. Biochar addition affected the soil chemical properties of the fertilized microcosms (ND and HD). Biochar increased the $\mathrm{N}{\mathrm{H}}_4^{+}$ content in HD soil and the $\mathrm{N}{\mathrm{O}}_3^{-}$ content in ND soil by 26 mg/L and 48.76 mg/L, respectively. The results showed that biochar application increased the marketable cauliflower yield. In ND+B and HD+B, the curd weight was 880.68 kg and 1097.60 kg, respectively. In addition, a small number of nitrogenous compounds in the leachate were quantified in experimental lines with the biochar. Therefore, biochar use improves the marketable yield of horticulture, mitigating the negative impacts associated with the mass use of N fertilizers in agriculture.